DFT study of the mechanism of hydroamination of ethylene with ammonia catalyzed by diplatinum(II) complexes: Inner- or outer-sphere?

A detailed analysis of the reaction profiles of the hydroamination reaction between ethylene and ammonia catalyzed by the diplatinum(II) [{Pt(NH2)(mu-H)(PPh3)}2] complex is presented herein using density functional theory computational techniques. The coordinatively unsaturated 14e T-shaped [Pt(NH2)(PPh3)H] species resulted from the dissociation of the diplatinum [{Pt(NH2)(mu-H)(PPh3)}2] precatalyst are identified as the active catalytic species. All possible reaction pathways that constitute the entire catalytic cycle have exhaustively been investigated. Overall, the rate-determining step of all catalytic cycles constructed was found to be the oxidative addition of ammonia that leads to the regeneration of the catalyst. According to the energy span model, the outer-sphere mechanism for the hydroamination of ethylene with ammonia catalyzed by the diplatinum complexes is favored over the inner-sphere one, whereas TOF values are in favor of the inner-sphere mechanism. (c) 2012 Wiley Periodicals, Inc.